Study Predicts Detection of Lyman-Alpha Scattering Signals from Early Universe Using JWST Data
Researchers have used JWST observations of early galaxies to predict the power spectrum of Loeb-Rybicki halos — diffuse glows of scattered Lyman-alpha light around galaxies before cosmic reionization. These halos form when Lyman-alpha photons scatter off neutral intergalactic hydrogen and Doppler-shift out of resonance as the universe expands. The findings suggest that upcoming instruments could statistically detect these signals, offering a new observational window into the universe's first billion years.
A study accepted for publication in Astronomy & Astrophysics uses inferred Lyman-alpha luminosity evolution of galaxies at redshifts z ~ 9–16, derived from JWST data, to forecast the detectability of so-called Loeb-Rybicki intergalactic halos. These halos arise when Lyman-alpha photons emitted by early galaxies scatter off neutral hydrogen in the expanding intergalactic medium until they Doppler shift out of resonance and escape toward the observer, producing extended diffuse emission. The authors calculate the clustering power spectrum of these halos and find strong prospects for statistical detection via intensity mapping with current and planned missions including SPHEREx and CDIM. Additionally, the study examines cross-correlation of this Lyman-alpha signal with 21-cm emission from neutral hydrogen, finding that the cross-correlation should be detectable at a significance of several to tens of standard deviations out to z ~ 13, and marginally out to z ~ 16, when combining SPHEREx or CDIM with the Square Kilometre Array-LOW and its precursor, the Murchison Widefield Array. The results suggest that intensity mapping of Loeb-Rybicki halos could become a powerful complementary probe of the pre-reionization epoch alongside 21-cm cosmology.
What's missing
The study's predictions rely on Lyman-alpha luminosity functions inferred from JWST data, which themselves carry observational uncertainties and model-dependent assumptions about galaxy properties at these redshifts. The analysis does not fully address potential contamination from foreground emission or the practical challenges of separating the Loeb-Rybicki halo signal from other diffuse backgrounds in real observations.
What different sources said
- arXiv astro-phCenter
Intensity mapping of Loeb-Rybicki haloes from scattering of galactic Lyman-$\alpha$ emission by the diffuse intergalactic medium before reionization
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